常用的一些自定义函数

 1         function $id()
 2         {
 3             var obj,name;
 4             if( arguments.length==2 )
 5             {    
 6                 obj = arguments[0];
 7                 name = arguments[1];
 8             }else if( arguments.length==1 ){
 9                 obj = document;
10                 name = arguments[0];
11             }else{
12                 return alert( "$id have error!" );
13             }
14             return obj.getElementById(name);
15         }
16         
17         function $selectedOption(obj,selectedValue)
18         {
19             for( var i=0;i<obj.options.length;i++ )
20             {
21                 if( obj.options[i].value == selectedValue )
22                 {
23                     obj.options[i].setAttribute("selected","true");
                       obj.selectedIndex = i; //这行代码是后来加上去的，原因在ＩＥ中找不到selectedIndex
24                     return;
25                 }
26             }
27         }
28         
29         function $name()
30         {
31             var obj,name;
32             if( arguments.length==2 )
33             {    
34                 obj = arguments[0];
35                 name = arguments[1];
                   return obj[name]!==undefined ? obj[name]:obj.getElementsByName(name);
36             }else if( arguments.length==1 ){
37                 obj = document;
38                 name = arguments[0];
                   return obj.getElementsByName(name);
39             }else{
40                 return alert( "$name have error!" );
41             }
43         }
44         
45         function $tag()
46         {
47             var obj,name;
48             if( arguments.length==2 )
49             {    
50                 obj = arguments[0];
51                 name = arguments[1];
52             }else if( arguments.length==1 ){
53                 obj = document;
54                 name = arguments[0];
55             }else{
56                 return alert( "$tag have error!" );
57             }            
58             return obj.getElementsByTagName(name);
59         }
60     
61         String.prototype.trim = function() {
62             var str = this,
63             str = str.replace(/^\\s\\s*/, ''),
64             ws = /\\s/,
65             i = str.length;
66             while (ws.test(str.charAt(--i)));
67             return str.slice(0, i + 1);
68         }